Gas-pressurized torrefaction of biomass wastes: Roles of pressure and secondary reactions

Abstract

A gas-pressurized (GP) torrefaction method, proposed in our resent work, can significantly promote the upgrading and oxygen removal of biomass wastes, compared to the traditional torrefaction (AP). However, the mechanism of the GP torrefaction process is not clear. In present work, semi-closed (SC) torrefaction, GP torrefaction, and AP torrefaction were conducted to reveal the roles of pressure and secondary reactions during GP torrefaction quantitatively. The results showed that the pressure significantly promoted the upgrading of biomass during GP torrefaction at 200 °C. The contribution of pressure on the oxygen removal of GP torrefaction at 200 °C was 63.87%. At relatively high temperature of around 250 °C, the promotions were caused by the synergistic effect of pressure and secondary reactions. The contribution of secondary reactions on the oxygen removal was 53.99%. Thus, the process of the GP torrefaction of biomass wastes was preliminarily understood.